This application claims benefit of Japanese Patent Application No. 2000-154719 filed on May 25, 2000, the contents of which are incorporated by the reference.
The present invention relates to telephone terminals and, more particularly, to letter message communication methods and apparatus in telephone terminals capable of transmitting and receiving letter messages.
Telephone terminals having a letter message communication function have various advantages over the telephone terminals for the sole voice communication, and can expand the scope of application of the communication means. As an example of the advantages obtainable with the letter message communication function, it is possible to permit telephone communication by hearing disabled persons as well and also permit reliable transmission of the will even in great noise circumstances. As another example, it is possible to accurately transmit names of places and persons to the opposite side. As a further advantage, it is possible to reliably discriminate different words of the same pronunciation. As a still further advantage, it is possible to make communication without possibility of irritating nearby persons (with noise or the like). As an yet further advantage, it is possible to transmit the will or to confirm the will of the opposite side of the communication.
In the prior art, telephone terminals having the letter message communication function and pertinent techniques are disclosed in, for instance, Japanese Patent Laid-Open No. 11-215568, Japanese Patent Laid-Open No. 2000-13527 and Japanese Patent Laid-Open No. 2000-78654. In a PHS terminal disclosed in the first mentioneperformed of the above prior art literatures, it is sought to permit letter message exchange during voice communication. In the case of currently popular letter message communication services, letter messages are usually transmitted while neither voice communication nor data communication is in force.
The above prior art techniques have some problems. Firstly, for transmitting a letter message during voice communication, it is necessary to tentatively interrupt the voice communication by making retention setting and once ending the voice communication. This is so because the transmission of a letter message during the voice communication requires the switching of the base station to a letter message reception mode. In addition, the letter message transmission requires control channel switching, and therefore it can not be performed concurrently with the voice communication. Secondly, the telephone terminal user may forget the transmission of a letter message, which is worked out in advance by himself or herself with a letter message editor. This may result when the user concentrates himself or herself in a different topic of conversation.